This invention is in the field of apparatuses and methods for manufacturing Fresnel lenses and in particular apparatuses and methods for extruding Fresnel lens angular segments from plastic.
Processes for extruding sheet plastic from raw plastic material such as ingots and pellets and the like are well known in the industry. Similarly, processes for extruding Fresnel lenses from plastic through the use of heat and roller equipment for the extrusion process and dies for impressing the facet grooves on the face of the lens are known in the industry.
The use of Fresnel lenses for solar collectors is also known in the industry. Economic, operational, and maintenance considerations dictate that the use of a larger collector for solar collection applications is desirable. When a Fresnel lens is to be used for a solar collector, this usually dictates that the solar collector cannot be constructed of a single lens. Also, in the manufacturing of the Fresnel lens, ordinarily a size limitation is dictated by the size of the rollers that are used for the production of the Fresnel lens. This then requires that a solar collector be constructed from a composite of Fresnel lens components. It is also found that the use of a generally circular shape for a Fresnel lens is desirable for solar collector applications. Because of facet groove orientation limitations and geometric sizing and shape limitations, the manufacturing of Fresnel lens components for a generally circular solar collector is problematic.
An object of the present invention is to provide an apparatus and a method for manufacturing Fresnel lens components for a generally circular solar collector that will provide for the matching of Fresnel lens facet grooves of the components with the desired overall pattern of the solar collector and will provide for economy in manufacturing, including the use of common size rollers and other common extrusion equipment and the minimization of material waste. For purposes of this application, the term “generally circular” shall be defined to include polygon shapes such as an octagonal or hexagonal shape which have sides which are roughly equidistant from the geometric center of the collector.